The objective of this study was to compare the dissolution behavior of tablets prepared from solid dispersions with and without drug-carrier interactions. Diazepam and nifedipine were used as model drugs. Two types of carriers were used; polyvinylpyrrolidone (PVP K12, K30 and K60) and saccharides (inulin 1.8 kDa, 4 kDa and 6.5 kDa). Solid dispersions with various drug loads were prepared by lyophilization. It was found that the drug solubility in aqueous PVP solutions was significantly increased indicating the presence of drug-carrier interaction while the drug solubility was not affected by the saccharides indicating absence of drug-carrier interaction. X-ray powder diffraction and modulated differential scanning calorimetry revealed that all solid dispersions were fully amorphous. Dissolution behavior of solid dispersion tablets based on either the PVPs or saccharides was governed by both dissolution of the carrier and drug load. It was shown that a fast drug dissolution of solid dispersions with a high drug load could be obtained with carrier that showed interaction with the drug.

Imatinib trough levels have been associated with its clinical effects. During chronic use of imatinib, CYP2C8 becomes an important metabolizing enzyme because of cytochrome P450 3A4 (CYP3A4) autoinhibition. Single nucleotide polymorphisms (SNPs) in CYP2C8 may affect imatinib trough levels. This study investigates the effect of common CYP2C8 polymorphisms [*1B (rs7909236), *1C (rs17110453), *3 (rs11572080 and rs10509681), and *4 (rs1058930)] on steady-state trough levels imatinib during chronic imatinib use in 43 patients with chronic myeloid leukemia or gastrointestinal stromal tumors. Standardized imatinib trough levels did not show a significant difference between wild-type and variant groups for any of the tested SNPs, but an association with age was found, with older patients having higher trough levels. This suggests that common CYP2C8 SNPs have no effect on the pharmacokinetics of imatinib.

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